Ferrari's Felipe Massa was a season-best fourth but Kimi Raikkonen made a tactical error and ended up 16th.

McLaren's world champion Lewis Hamilton will start in 14th, with local hero Fernando Alonso's Renault eighth.

Button, who has won three of this season's first four races to establish a 12-point lead over Barrichello for dominant Brawn, has put himself in a strong position to add to that tally - the past eight Circuit de Catalunya pole-sitters have gone on to win the race.

BBC SPORT'S FUEL-ADJUSTED GRID (with projected race first pit stops*)

1 Vettel - 0.000 (lap 16)

2 Button - 0.059 (lap 14)

3 Massa - 0.151 (lap 17)

4 Barrichello - 0.172 (lap 15)

5 Webber - 0.389 (lap 16)

6 Trulli - 0.454 (lap 18)

7 Glock - 0.762 (lap 14)

8 Alonso - 0.959 (lap 13)

9 Rosberg - 1.321 (lap 23)

10 Kubica - 1.728 (lap 19)

* Calculated on the weight of fuel left in cars after qualifying had finished

He did so in tight fashion, sneaking ahead of Vettel at the last opportunity with a time of one minute 20.527 seconds as he and the German both went quicker than Kimi Raikkonen's 2008 lap record.

"An unexpected but very pleasing pole position today, probably my most satisfying pole of the season," said the 29-year-old.

"I just got across the line [to go out on my last lap] with a couple of seconds to spare.

"It was by far the best lap I've had all weekend. All weekend, Rubens has been tremendous and I've found it very hard to hang onto him on low fuel.

"I got the lap on the high fuel so I'm very happy. I just got to hope I can stay there on Turn One. It was a bit of a surprise so when I realised [I had pole], it felt very good."

When the weights of the cars in qualifying were published, it emerged that Vettel had been running with slightly more fuel than frontrunner Button - meaning that he was effectively the fastest man in the field.

Such calculations also mean Massa can be adjudged the third fastest, as he was carrying more fuel than Barrichello.

For Red Bull, who sit second in the constructors' championship, their season goes from strength to strength and Vettel's team-mate Mark Webber will start Sunday's race fifth on the grid.

Most teams have come into the first of nine European races with important upgrade packages to their cars, though judgement on how they have responded so far is mixed.

After qualifying, Hamilton was unequivocal when BBC Sport asked whether his McLaren upgrade package had improved his cars performance in any way.

"No", he said, adding: "I guess it's a bit of a disappointing qualifying for us.

Qualifying drivers news conference

"We did the best we could but the laps weren't fantastic. We had hoped to be higher up.

"It's not last and there's lots that can happen. It's a long tough race. I hope we can get a point, that would be great."

Toyota, third in the championship, are one of the minority not to have added to their car - which has served them well so far - and drivers Timo Glock and Jarno Trulli are sixth and seventh on the grid.

Ferrari's new aerodynamics package put Massa - who lost out on the world title last year to Hamilton by just one point - back in touch with the leaders after picking up only three points from the first four races for its worst ever start to a season.

And Button said that, with Ferrari using the energy recovery and boost system (Kers), the Brazilian could be in contention for a first victory of the season.

"I don't think anyone's gone that much faster than the Ferrari. They're quick," he said.

"I think we have the legs on them but they're closing quickly and I'm surprised."

Yet the reigning constructors' champions failed to see Raikonnen get through the first qualifying session as they made a repeat of the pit lane miscalculation which saw Massa suffer the same early exit in Malaysia.

Finnish driver Raikkonen, whose last GP race victory came last year in Spain, watched from the garage as Trulli knocked him out of contention as Ferrari's confidence in his time proved to be misplaced.

Hamilton's team-mate Heikki Kovalainen is 18th on the grid and McLaren appear to have slipped back from their competitors after the signs of improvement they showed in Bahrain, where both drivers made it through to the top ten in qualifying.

"[There was] just not enough pace," said Kovalainen, who played down the impact of being slightly held up by a BMW Sauber car at one point.

"I was trying to do the best I could as always but it was not enough.

"The car is just lacking grip and I didn't have the confidence to push any harder."

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